In automatic foundry machines for the manufacture of castings in sand moulds it is known to perform the pouring while the casting moulds are carried on a conveyor on which the filled casting moulds are advanced to a knocking-out station provided with a grid. On this grid, the castings are separated from the mould material which drops down through the grid and is returned to the mould production apparatus. The intense heat from the metal poured damages the mould sand which therefore must be regenerated between the successive applications. As a rule, for the purpose of regeneration, a certain percentage of the mould sand is removed on its way from the knocking-out grid to the mould production apparatus and is substituted by unused material, which is mixed thoroughly with the remaining part of the mould sand, possibly with the addition of special components for improving the properties of the mould sand in various respects.
Prior art foundry machines of this type cause a great deal of inconvenience, such as a high noise level and development of dust, heat and smell.
A particular problem arises in connection with casting moulds comprising one or more cores. The binding or bonding agent used in such cores consists increasingly of artificial resins that are thermally destroyed by heat from the poured metal so as to loose their binding effect in order to allow the core material to flow freely out of the cavities when the castings are knocked out of the moulds. When using such cores, the need for regeneration of the mould material is substantially increased because the material may comprise a rather great proportion of core sand devoid of active binder. Accordingly, in the regeneration step an appropriate quantity of new binder must be added and must be carefully admixed into the used mould material, and the regeneration step must also include withdrawal or removal of a portion of used material similar to the portion added as core material.
In the following specification the terms mould sand and mould material should be understood to include the material of any cores incorporated in the moulds.